CHICAGO (Reuters) - Using DNA, the blueprint of life, U.S.
researchers said they have made a three-dimensional structure
from particles of gold in a development that could lead to a
host of custom-designed materials.

The technique helps solve a basic problem in nanoscience:
getting impossibly small particles to assemble themselves
according to a predetermined design.

"We're using inspiration from life to create new forms of
matter," said Chad Mirkin, director of Northwestern
University's International Institute for Nanotechnology in
Evanston, Illinois. "It's a real example of man over nature."

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The idea takes advantage of the molecular biology of DNA,
in which one strand of DNA forms a bond with a complementary
strand to make what is called a base pair.

Mirkin and colleagues simply design the specific genetic
code using the four building blocks of DNA -- adenine, guanine,
cytosine and thymine or A, G, C and T -- and attach the gold
particles to those strands.

"Think of it as taking a set of particles, modifying them
with short strands of DNA and making those particles like
chemically specific Velcro," Mirkin said in a telephone
interview.

"I can add complementary strands of DNA that bind with one
another in preconceived and highly designed ways."

The researchers used double-stranded DNA in each particle,
with one of the strands significantly longer than the other.

When they place these designer particles in water, the
single-stranded portion of the DNA seeks out and binds to
partner strands to form the double-helix structure in a process
known as hybridization.

"It's the ultimate in this idea of self-organization. You
sprinkle in a bit of complementary DNA and the DNA does the
work," said Mirkin, whose research appears in the journal
Nature.

"The particles are bouncing off one another until they find
others to make the golden handshake," he said.

"By using the right kinds of codes, I can use those
particles to assemble into different forms of matter."

The end result is a three-dimensional structure or crystal,
in this case formed with gold particles.

"These are nano nuggets of gold, 13 billionths of a meter
in diameter. That is simply the core inorganic material we
used," he said. His team made two different crystal structures
by changing the genetic sequence.

In a related paper in Nature, researchers at the U.S.
Department of Energy's Brookhaven National Laboratory report
using these same complementary properties of DNA to make a
crystalline structure using gold nanoparticles.

Borrowing from techniques used for making traditional
crystals, the team then heated the DNA-linked particles and
cooled them, allowing the particles to form more stable
arrangements.

"This work is the first step to demonstrate that it is
possible to obtain ordered structures. But it opens so many
avenues for researchers, and this is why it is so exciting,"
Oleg Gang, a researcher at Brookhaven's Center for Functional
Nanomaterials, said in a statement.

Both teams said the process could be used with other
materials, offering applications in drugs, diagnostics, optics
and electronics.

Mirkin said the research brings scientists a step closer to
the dream of breaking everything down into fundamental
particles and reassembling them into "designer" structures.